Container, thermo-molding apparatus and method for thermo-molding the same

ABSTRACT

The present invention provides a bottomed cylindrical container, comprising a body wall, a bottom wall, and a ring-shaped foot downwardly extending from the bottom wall, said container being produced by thermo-molding a resin sheet, characterized in that said foot is formed by folding an inner wall by compressed fluid to be fusion-bonded with an outer wall, so as to form the foot comprising the inner wall and the outer wall. The present invention also provides a bottomed cylindrical container, comprising a body wall having a grounding edge at a lower end thereof, and a bottom wall, said container being produced by thermo-molding a resin sheet, characterized in that said bottom wall connects with an upper edge of an inner wall produced by folding back the body wall along the grounding edge and by fusion-bonding it to an inner periphery of the body wall. In addition, the present invention provides the methods for thermo-molding these containers and their apparatuses.

This is a Division of application Ser. No. 10/491,959 filed Apr. 8,2004, which in turn is a National Stage of International Application No.PCT/JP02/11284 filed Oct. 30, 2002. The disclosure of the priorapplications is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

This invention relates to a container and a thermo-molding apparatus anda thermo-molding method for molding such a container. More particularly,the present invention relates to a legged and bottomed cylindrical thinwall container or a bottomed cylindrical container having the bottomwall connected to the inner barrel of the body section produced byfolding the latter back at the grounding edge of the container, which ismolded by thermo-molding and made free from any gap in the inside of thejunction of the leg or the body inner barrel and the body wall, and alsoa thermo-molding apparatus and a thermo-molding method for molding sucha container.

Legged and bottomed containers molded by thermo-molding a thermoplasticresin sheet and made free from any gap in the inside at the sitecorresponding to the leg shaped by bending the sheet and thermo-moldingapparatus and thermo-molding methods for molding such bottomedcontainers are known to date. For example, Japanese Patent Laid-openNos. 2000-225642 and 2001-001395 disclose such bottomed containers andthermo-molding apparatus and thermo-molding methods for molding suchbottomed containers.

According to the above patent documents describing the prior art, abottomed container is thermo-molded either by using a thermo-moldingapparatus comprising an upper plug unit having a pressure molding plugand cooling male mold, and a unit of female mold including an upper moldfor forming the mouth section and the body peripheral section of thecontainer, an intermediate mold for forming the lower part of the bodyperipheral section and the outer peripheral surface of the bottom rim(or foot) and a bottom mold for forming the inner peripheral surface ofthe bottom rim and the bottom wall or by using a thermo-moldingapparatus comprising a pressure molding plug, a female mold and a bottommold.

More specifically, a container is molded by pushing the pressure moldingplug into the female mold to shape the container so as to make it showthe profile of the surface of the female mold, while holding the bottommold to the lowered position, and subsequently raising the bottom moldto form the bottom wall and the bottom rim respectively on the uppersurface of the bottom mold and between the bottom mold and the femalemold.

The bottom rim is made either to flare toward the lower end and show atriangular cross section or to show a cylindrical profile that isvertically extending with a same diameter.

With the prior art, regardless if the bottom rim is flared or made toshow a vertically extending cylindrical profile, the difference betweenthe outer diameter of the upper end of the mold surface of the femalemold (more particularly its intermediate mold) for forming the outerperipheral surface of the bottom rim and the outer diameter of the moldsurface of the bottom mold for forming the inner peripheral surface ofthe bottom rim is greater than the thickness of the resin sheet andslightly smaller than the twice of the thickness because the bottom rimis formed between the mold surface of the mold surface of the femalemold (more particularly its intermediate mold) and that of the bottommold.

Therefore, if twice of the resin sheet that is used for producing thecontainer is smaller than the difference of the diameters, a gap isproduced along the inner surface of the container at the site thatcorresponds to the bottom rim.

This means that, with either of the above described thermo-moldingapparatus and the corresponding molding method, it is not feasible touse resin sheets having different thicknesses and particularly thinresin sheets cannot be used.

If thin resin sheets are to be used, the difference between the outerdiameter of the upper end of the mold surface of the female mold (moreparticularly its intermediate mold) for forming the outer peripheralsurface of the bottom rim and the outer diameter of the mold surface ofthe bottom mold for forming the inner peripheral surface of the bottomrim needs to be reduced.

Additionally, the thickness of resin sheet can show variances in thestages before forming the bottom rim because the thickness of theoriginal roll, the thermo-molding temperature, the degree of vacuum andthe timing of applying compressed air can vary significantly. Therefore,it is very difficult to constantly maintain the molding conditions thatmake the thickness of the bent resin sheet slightly greater than the gapbetween the metal molds.

Thus, while the above described problem may be relatively insignificantwhen molding a large container by using a thick resin sheet, thethickness may have to be more rigorously controlled when a relativelythin resin sheet is used. In other words, the prior art is not suitedfor molding small containers.

SUMMARY OF THE INVENTION

Therefore, it is the object of the present invention to dissolve theabove identified problem and provide a legged and bottomed cylindricalcontainer having no gap in the inside of the foot or a bottomedcylindrical container having no gap between the inner barrel of the bodyproduced by bending the original resin sheet at the grounding edge andthe body wall, a thermo-molding apparatus and a thermo-molding methodfor molding such a container.

According to the invention, the above object is achieved by providing abottomed cylindrical container, comprising a body wall, a bottom wall,and a ring-shaped foot downwardly extending from the bottom wall, saidcontainer being produced by thermo-molding a resin sheet; characterizedin that said foot is formed by folding an inner wall by compressed fluidto be fusion-bonded with an outer wall, so as to form the footcomprising the inner wall and the outer wall. Preferably, said bottomwall comprises a central section and a peripheral section, and theperipheral portion is made thin.

According to another aspect of the invention, the above object isachieved by providing a bottomed cylindrical container, comprising abody wall having a grounding edge at a lower end thereof, and a bottomwall, said container being produced by thermo-molding a resin sheet,characterized in that said bottom wall connects with an upper edge of aninner wall produced by folding back the body wall along the groundingedge and by fusion-bonding it to an inner periphery of the body wall.

The present invention also provides an apparatus for thermo-molding aresin sheet to a bottomed cylindrical container, comprising an uppermold having a plug, and a lower mold having a female mold and a bottombush; wherein said female mold has mold surfaces for forming a body wallof the container; and said bottom bush has compressed air blow-in holes.Also, it provides an apparatus for thermo-molding a resin sheet to abottomed cylindrical container with a ring-shaped foot, comprising anupper mold having a plug, and a lower mold having a female mold and abottom bush, wherein; said female mold is provided with suction holes;said female mold has a mold surface for forming a body wall of thecontainer, a mold surface for forming a bottom peripheral wall of thecontainer, and a mold surface for forming an outer wall of the foot; andsaid bottom bush has compressed fluid blow-in holes. Preferably, saidlower mold comprises a mold base, the bottom bush in the mold base, andthe female mold on the mold base; a gap is formed between a lowersurface of the female mold and the mold base; and an annular suctiongroove is formed between a lower surface of the female mold and the moldbase, and communicates with the gap.

Another aspect of the present invention provides a method forthermo-molding a footed and bottomed cylindrical container; comprisingheating a thermoplastic resin sheet; pressing the heated sheet by a plugof an upper mold with vacuum-sucking, to contact the sheet with moldsurfaces of a female mold of a lower mold, so as to form a body wall andan outer wall of a foot of the container; and blowing compressed fluidthrough blow-in holes of a bottom bush of the lower mold into the femalemold with vacuum-sucking, to contact the sheet on a top surface of thebottom bush with a bottom surface of the plug, so as to form a bottomwall and an inner wall of the foot, said inner wall being fusion-bondedwith the outer wall.

Still another aspect of the present invention provides a method forthermo-molding a bottomed cylindrical container; comprising heating athermoplastic resin sheet; pressing the heated sheet by a plug of anupper mold with vacuum-sucking, to contact the sheet with mold surfacesof a female mold of a lower mold, so as to form a body wall of thecontainer; and blowing compressed fluid through blow-in holes of abottom bush of the lower mold into the female mold with vacuum-sucking,to contact the sheet on a top surface of the bottom bush with a bottomsurface of the plug, so as to form a bottom wall and an inner wall beingfusion-bonded with the body wall.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic front view of the first embodiment of legged andbottomed container according to the invention, showing it partly incross section. FIG. 1B is an enlarged partial view of the embodiment,showing a principal part thereof.

FIG. 2 is a schematic front view of the first embodiment ofthermo-molding apparatus according to the invention, showing it partlyin cross section.

FIG. 3 is a schematic front view of the first embodiment ofthermo-molding apparatus of FIG. 2, showing it partly in cross sectionand illustrating the state where the molds are closed and the plug ismade to start lowering.

FIG. 4A is a schematic front view of the first embodiment ofthermo-molding apparatus of FIG. 2, showing it partly in cross sectionand illustrating the state where the plug reaches the lowest positionand the vacuum molding operation is completed. FIG. 4B is an enlargedpartial view of the embodiment of FIG. 4A.

FIG. 5 is a schematic front view of the first embodiment ofthermo-molding apparatus of FIG. 2, showing it partly in cross sectionand illustrating the state the bottom of the container is molded byapplying compressed air.

FIG. 6 is a schematic front view of the first embodiment ofthermo-molding apparatus of FIG. 2, showing it partly in cross sectionand illustrating the state where the operation of molding the bottom ofthe container by applying compressed air is completed.

FIG. 7 is a schematic front view of the second embodiment of legged andbottomed container according to the invention, showing it partly incross section.

FIG. 8 is a schematic front view of the second embodiment ofthermo-molding apparatus, showing it partly in cross section andillustrating the state where the plug reaches the lowest position andthe vacuum molding operation is completed.

FIG. 9 is a schematic front view of the second embodiment ofthermo-molding apparatus of FIG. 8, showing it partly in cross sectionand illustrating the state where the operation of molding the bottom ofthe container by applying compressed air is completed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, the present invention will be described in detail by referring tothe accompanying drawings that illustrate preferred embodiments of theinvention.

Firstly, the first embodiment of footed and bottomed cylindricalcontainer or footed bowl-shaped container A will be described.

As shown in FIG. 1, a footed and bottomed cylindrical container Acomprises a body wall 2 having an outwardly directed flange 1 arrangedalong a peripheral edge of a top opening, a bottom wall 3, and aring-shaped foot 4 extending downwardly from the bottom wall 3.

The body wall 2 is curved inwardly at and near a lower end thereof untilit becomes horizontal and reaches to the foot 4. Such horizontal part isa bottom peripheral wall 5 which connects to the bottom wall 3. Thebottom wall 3 is located within the foot 4, and comprises a centralsection 6 a and a thin peripheral section 6 b.

The foot 4 comprises an outer wall 7 a and an inner wall 7 b which isproduced by inwardly folding back the outer wall 7 a along at a loweredge thereof and welded to the outer wall. An outwardly bulge 8 isformed along a lower peripheral edge of the foot 4.

Preferable resin materials that can be used for forming the container Ainclude poly-olefin type resins such as polypropylene (PP) andpolyethylene (PE), although other thermo-moldable synthetic resinmaterials or thermoplastic resin material such aspolyethyleneterephthalate (PET) can also suitably be used. The syntheticresin sheet to be used for molding may be of single layer or ofmultilayer (or laminate).

The synthetic resin sheet to be used for molding has a thickness between0.3 and 3.0 mm, while the wall thickness of the body wall of thecontainer obtained by thermo-molding the sheet is between about 0.1 andabout 0.45 mm.

Now, the first embodiment of thermo-molding apparatus B to be used forthermo-molding the first embodiment of container will be described.

As shown in FIG. 2, the thermo-molding apparatus B comprises an uppermold C and a lower mold D.

The upper mold C comprises a cylindrical clamp 11 for pinching the sheetS, and a plug 10 vertically movable relative to the clamp 11. The sheetS is heated by a heater (not shown). The clamp 11 is not limited tocylindrical shape.

The plug 10 has a cylindrical wall surface 12 and a flat bottom surface13. While the clamp 11 is so designed that compressed fluid (such ascompressed air) is blown into it from above, it is not essential to blowcompressed fluid into the clamp 11.

While the plug 10 of the illustrated embodiment shows a cylindricalprofile, it may alternatively show some other profile such a conicalprofile. Similarly, while the bottom surface 13 of plug of theillustrated embodiment is flat, it may alternatively be outwardly orinwardly curved depending on the molded product to be produced by usingit.

The lower mold D comprises a mold base 15, a female mold 16 arranged onthe mold base 15, and a bottom bush 17 arranged in an inside of the moldbase 15.

The female mold 16 has a mold surface 18 for forming the body wall 2 ofthe container A to be molded, a mold surface 19 for forming the bottomperipheral wall 5, and a mold surface 20 for forming the outerperipheral surface of the foot 4. A passage 21 is arranged at the lowerperipheral edge of the mold surface 20, so that a gap 21 is providedbetween the lower surface of the female mold 16 and the mold base 15.The gap 21 communicates with an annular suction groove 22.

The suction groove 22 communicates with a connection hole 23 arranged inthe mold base 15. The connection hole 23 communicates with a vacuum unit(not shown). The female mold 16 is provided with a communication hole24. The communication hole 24 communicates with the connection hole 23.A number of suction holes 25 are arranged near the upper edge and alongthe lower edge of the mold surface 18 of the female mold 16, and each ofthe suction holes 25 communicates with the communication hole 24. Thus,air can be drawn from the inside of the female mold 16 through theconnection hole 23, the suction groove 23, the gap 21 and the suctionholes 25.

A number of blow-in holes 27 are formed at a center of the top surface26 of the bottom bush 17. A connection hole 28 is formed in the bottombush 17, and communicates with a source of compressed fluid (not shown).Thus, compressed fluid is blown into the inside of the female mold 16through the communication hole 28 and the blow-in holes 27.

The bottom bush 17 is provided with a heater 29.

Now, the method of thermo-molding the container according to the firstembodiment of the invention will be described below.

For the purpose of thermo-molding, the sheet S is heated by a heater(not shown) to the molding temperature that is somewhat lower than amelting point of the synthetic resin. The female mold 16 and the bottombush 17 of the thermo-molding apparatus B are also heated and maintainedto a predetermined temperature level (usually about 80 to about 150° C.,about 50 to about 180° C. depending on the material of the sheet) by theheater 29. In this case, the temperature of the female mold 16 and thebottom bush 17 should be controlled not to cool the heated sheet.

If the resin sheet S is made of PP and has a thickness of 1.0 mm, it isheated to about 140 to 200° C.

The upper mold C is lowered, and the lower mold is raised from the stateof FIG. 2. As shown in FIG. 3, the heated sheet becomes pinched andpressed between the clamp 11 of the upper mold C and the top surface ofthe female mold 16 of the lower mold D. The plug 10 is further loweredrelative to the clamp 11, the sheet S is forced to extend downwardly bythe lower surface 13 of the plug 10, because the sheet is already heatedand softened. At this time, since air is drawn through the gap 21 andthe suction holes 25, the sheet S is drawn by the suction holes 25, andcomes to be held in tight contact with the inner surface of female moldabove the suction holes 25. At this time, compressed fluid may be blowninto the clamp 11 from above.

When the plug 10 is further lowered, the sheet S comes to be held intight contact with the mold surfaces 18, 19, 20 of the female mold 16and the top surface 26 of the bottom bush 17, as illustrated in FIG. 4.Thus, the sheet S is molded by the mold surfaces 18, 19, 20 and the topsurface 26, to produce the body wall 2, the bottom peripheral wall 5 andthe outer wall 7 a of the foot 4 of the container A.

As shown in FIGS. 4A and 4B, the plug 10 is stopped before it contactswith the mold surface 19. As a result, a gap is formed between the sheetS on the mold surface 19 and the lower surface 13 of the plug 10. Air isdrawn out through the gap when compressed air is blown into the femalemold 16 in a subsequent step as will be described hereinafter. In thecase of the illustrated embodiment, the gap is about 0.1 to 0.5 mm.

By the above described vacuum sucking, resin “a” is drawn into the gap21 to produce the bulge 8 of the container. Since the resin “a” is drawninto the gap 21, the gap 21 is filled with the resin, so that eventuallyno resin is further drawn into the gap 21 any more. The bottom bush 17is heated to the above described predetermined temperature level by theheater 29, and the part of the sheet S that contacts with the topsurface 26 of the bottom bush 17 is held to the molding temperature thatis close to the melting point.

As described above, the sheet S is pressed and held in contact with themold surface 19 as a result of the air suction through the suction holes25 for producing vacuum (and due to the compressed air in the clamp 11,if desired), the resin “a” of the lower end of the sheet S is drawn intothe gap 21, and the part of the sheet S that is held in contact with thetop surface 26 is held to the molding temperature that is close to themelting point. Under these circumstances, when compressed fluid is blowninto the female mold 16 through the blow-in holes 27, the part of thesheet S with the temperature level close to the melting point is foldedback along the lower edge of the outer wall 7 a, and is moved upwardly,as illustrated in FIG. 5. Thus, the central portion of the part of thesheet S with the temperature level close to the melting point is broughtinto tight contact with the bottom surface 13 of the plug 10, while theperipheral portion is folded back along the lower edge of the outer wall7 a, and drawn to come into tight contact with and fusion-bonded to theouter wall 7 a. In this way, the foot 4 is formed by fusion-bonding theouter wall 7 a and the inner wall 7 b as integral parts thereof. FIG. 6schematically illustrates a state where the operation of producing thefooted and bottomed cylindrical container by molding is completed.

At this time, since the peripheral part of the sheet S is expanded, theperipheral section 6 b of the molded bottom wall 3 shows a thicknesssmaller than the central section 6 a. Besides, since the temperature ofthe sheet is maintained to a level close to the melting point, thefolded portion is fusion-bonded to the portion of the sheet S that isheld in tight contact with the mold surface 20.

The central section can be made thin by using a plug having an upwardlycurved lower surface for the molding operation using compressed air.

The thus formed container A is then cooled, and removed from the mold.Subsequently, the outwardly directed flange 1 is formed by cutting in adesired profile, to complete the operation of producing the footed andbottomed cylindrical container A.

The inner wall 7 b and the outer wall 7 a of the foot 4 of the obtainedcontainer A are in a completely fusion-bonded. In other words, they areintegrally formed without any gap. It is a thin wall container whosebody wall 2 and the bottom wall 3 are about 0.2 mm thick.

The above described first embodiment can be modified as follows.

In the above described embodiment, the plug 10 is stopped before itcontacts the mold surface 19 of the female mold 16, and a gap is formedbetween the sheet S on the mold surface 19 and the lower surface 13 ofthe plug 10, to allow the air (between the sheet S on the bush 17 andthe lower surface 13) left there to be drawn out. Alternatively, theplug 10 may be replaced by a plug 10 having a vent arranged between thelower surface 13 and the cylindrical wall surface 12. In suchmodification, the lower surface 13 of the plug 10 presses the sheet Sagainst the mold surface 19 for forming the bottom peripheral wall.

When the compressed fluid is blown through the blow-in holes 27 in thismodified embodiment, air between the sheet S on the bottom bush 17 andthe bottom surface 13 can be removed by the above described vent.

Still alternatively, if the bottom surface 13 of the plug 10 is stoppedfurther before the mold surface 19 of the female mold 16 to produce agap of 0.5 to 1.5 mm between itself and the sheet surface after thevacuum forming, and if the compressed fluid is blown through the blow-inholes 27, the bottom wall 3 will project above the bottom peripheralwall 5 by pressure forming.

Now, the second embodiment of the container, the thermo-moldingapparatus and the thermo-molding method to be used for molding thecontainer will be described below.

This embodiment of the invention relates to a bottomed cylindricalcontainer (cup-shaped container).

Referring to FIG. 7, A′ denotes the bottomed cylindrical container thatcomprises a body wall 31 having an outwardly directed flange 30 arrangedalong a peripheral edge of the opening, and a bottom wall 32.

A lower end of the body wall 31 is a grounding edge 33 of the container.The body wall 31 is inwardly folded back along the grounding edge 33 toproduce an inner wall 34. A top edge 35 of the inner wall 34 connects tothe bottom wall 32.

The inner wall 34 is fusion-bonded or welded to an inner periphery ofthe part of the body wall 31 located under the top edge 35, and no gapis found between the body wall 31 and the inner wall 34.

The method of thermo-molding the container according to the secondembodiment of the invention will be described below.

The thermo-molding apparatus in the second embodiment is obtained bymodifying the lower mold of the first embodiment of the invention.Therefore, the components that are same as those of the first embodimentare denoted by the same reference numerals and affixed by “a”. Thedifferences of the second embodiment and the first embodiment will bedescribed specifically.

Referring to FIG. 8, reference symbol C′ denotes the upper mold, and D′denotes the lower mold.

As in the case of the above described first embodiment, the upper moldC′ comprises a cylindrical clamp 11 a and a plug 10 a vertically movablerelative to the clamp 11 a. The sheet S′ is heated by a heater (notshown). The plug 10 a has a cylindrical wall surface 12 a and a flatbottom surface 13 a. While the clamp 11 a is so designed that compressedfluid (such as compressed air) is blown into it from above, it is notessential to blow compressed fluid into the clamp 11 a.

The lower mold D′ comprises a mold base 15 a, a female mold 16 aarranged on the mold base 15 a, and a bottom bush 17 a arranged in aninside of the mold base 15 a.

The female mold 16 a has a mold surface 40 for forming the body wall 31of the container A′ to be molded. A passage 21 a is arranged at thelower peripheral edge of the mold surface 40, so that a gap 21 a isprovided between the lower surface of the female mold 16 a and the moldbase 15 a. The gap 21 a communicates with an annular suction groove 22a, which suction groove 22 a communicates with a vacuum device (notshown).

A number of blow-in holes 27 a are formed at a center of the top surface26 a of the bottom bush 17 a. The blow-in holes 27 a communicate with asource of compressed fluid (not shown).

The bottom bush 17 a is provided with a heater 29 a.

Now, the method of thermo-molding the container according to the secondembodiment of the invention will be described below.

For the purpose of thermo-molding, the sheet S′ is heated by a heater(not shown) to the molding temperature that is somewhat lower than themelting point of the synthetic resin. The female mold 16 a and thebottom bush 17 a of the thermo-molding apparatus B′ are also maintainedto the above described predetermined temperature level by the heater 29a.

The heated sheet S′ is pinched and pressed between the clamp 11 a of theupper mold C′ and the top surface of the female mold 16 a of the lowermold D′. The plug 10 a is further lowered relative to the clamp 11 a,the sheet S′ is forced to extend downwardly by the lower surface 13 a ofthe plug 10 a, because the sheet is already heated and softened. At thistime, compressed air is blown from the above, and air is drawn throughthe gap 21 a on the lower surface of the female mold 16 a to producevacuum, so that the sheet S′ is drawn by the gap 21 a. As a result, thesheet S′ comes to be held in tight contact with mold surface 40 offemale mold 16 a.

The plug 10 a is further lowered and stopped before it contacts with themold surface 40 of the female mold 16 a, as shown in FIG. 8. As aresult, the sheet S′ is brought into tight contact with the mold surface40 of the female mold 16 a and the top surface 26 a of the bottom bush17 a, and molded to show a profile defined by the mold surface 40 of thefemale mold 16 a and the top surface 26 a of the bottom bush 17 a. Atthis time, the sheet produces portions that become the body wall 31 andthe bottom wall 32 of the container A′.

As in the case of the above described first embodiment, resin a is drawninto the gap 21 a by the air drawing operation or the vacuum sucking.The bottom bush 17 a is heated to the above described predeterminedtemperature level by the heater 29 a. The part of the sheet thatcontacts with the top surface 26 a of the bottom bush 17 a is held tothe molding temperature that is close to the melting point.

In this way, by the vacuum sucking and the compressed fluid, the sheetS′ is pressed between the mold surface 40 and the top surface 26 a ofthe bottom bush 17 a, and the resin “a” of the lower end portion of thebody wall 31 of the sheet S′ is drawn into the gap 21 a. Then, as shownin FIG. 9, compressed air is blown into through the blow-in holes 27 aof the bottom bush 17 a. The portion of the sheet held on the topsurface 26 a is folded back along the grounding edge 33. In this case,the central portion of the sheet is brought into tight contact with thebottom surface 13 a of the plug 10 a, while the peripheral portion ofthe sheet is brought into tight contact with and fusion-bonded to theinner peripheral surface of the body wall 31. Thus, as shown in FIG. 7,a bottomed cylindrical container A′ whose inner wall 34 produced byfolding back along the grounding edge 33 of the body wall 31 isfusion-bonded to the body wall 31 is obtained.

The present invention provides the following advantages.

A footed and bottomed cylindrical container according to the inventiondoes not have any gap on the inner surface of the container at a sitecorresponding to the foot where food can enter.

In a bottomed cylindrical container according to the invention, theinner wall produced by folding back the body wall along the groundingedge thereof is welded to the body wall and hence no gap where food canenter is produced there.

When a bottomed cylindrical container according to the invention isfilled with hot food, sealed and then cooled to reduce the innerpressure, the bottom wall of the container operates to absorb the impactof pressure reduction to prevent any deformation or recession of thesealed surface because the container has a thin the bottom wall, or atleast a then peripheral portion in the bottom wall.

Since a thermo-molding method and a thermo-molding apparatus accordingto the invention is adapted to mold a ring-shaped foot or a bottom wallby using compressed air and welding the resin layer of the innerperipheral portion and that of the outer peripheral portion of the footfor a bottomed cylindrical container, the foot is formed without gap ifthe thickness of the material resin sheet fluctuates. Similarly, sincethe inner wall produced by folding back the body wall along thegrounding edge thereof and welded to the body wall for a cup-shapedcontainer, no gap is formed between the body wall and the inner wall ifthe thickness of the material resin sheet fluctuates.

Therefore, containers showing a same profile can be produced by usingdifferent material resin sheets that may have different thicknesses bymeans of a same thermo-molding apparatus.

Thus, containers having a small wall thickness can be produced by usinga thin material resin sheet to save the material depending on theapplications of the containers.

Since the present invention imposes no restrictions on the thickness ofthe material resin sheet, a bottomed cylindrical container can beproduced simply by bringing the bottom surface of the plug of athermo-molding apparatus according to the invention into contact with orclose to the mold surface of the peripheral wall of the bottom of thefemale mold of the apparatus regardless of the size of container.

Small containers can be produced by using a thin material resin sheet.

1-3. (canceled)
 4. A method for thermo-molding a footed and bottomedcylindrical container, comprising: heating a thermoplastic resin sheet,pressing the heated sheet by a plug of an upper mold withvacuum-sucking, to contact the sheet with mold surfaces of a female moldof a lower mold, so as to form a body wall and an outer wall of a footof the container, and blowing compressed fluid through blow-in holes ofa bottom bush of the lower mold into the female mold withvacuum-sucking, to contact the sheet on a top surface of the bottom bushwith a bottom surface of the plug, so as to form a bottom wall and aninner wall of the foot, said inner wall being fusion-bonded with theouter wall.
 5. A method for thermo-molding a bottomed cylindricalcontainer, comprising: heating a thermoplastic resin sheet, pressing theheated sheet by a plug of an upper mold with vacuum-sucking, to contactthe sheet with mold surfaces of a female mold of a lower mold, so as toform a body wall of the container, and blowing compressed fluid throughblow-in holes of a bottom bush of the lower mold into the female moldwith vacuum-sucking, to contact the sheet on a top surface of the bottombush with a bottom surface of the plug, so as to form a bottom wall andan inner wall being fusion-bonded with the body wall.
 6. (canceled)